tutorial/lesson_03_debugging_1.cpp

// Halide tutorial lesson 3: Inspecting the generated code
 
// This lesson demonstrates how to inspect what the Halide compiler is producing.
 
// On linux, you can compile and run it like so:
// g++ lesson_03*.cpp -g -I <path/to/Halide.h> -L <path/to/libHalide.so> -lHalide -lpthread -ldl -o lesson_03 -std=c++17
// LD_LIBRARY_PATH=<path/to/libHalide.so> ./lesson_03
 
// On os x:
// g++ lesson_03*.cpp -g -I <path/to/Halide.h> -L <path/to/libHalide.so> -lHalide -o lesson_03 -std=c++17
// DYLD_LIBRARY_PATH=<path/to/libHalide.dylib> ./lesson_03
 
// If you have the entire Halide source tree, you can also build it by
// running:
//    make tutorial_lesson_03_debugging_1
// in a shell with the current directory at the top of the halide
// source tree.
 
#include "Halide.h"
#include <stdio.h>
 
// This time we'll just import the entire Halide namespace
using namespace Halide;
 
int main(int argc, char **argv) {
 
    // We'll start by defining the simple single-stage imaging
    // pipeline from lesson 1.
 
    // This lesson will be about debugging, but unfortunately in C++,
    // objects don't know their own names, which makes it hard for us
    // to understand the generated code. To get around this, you can
    // pass a string to the Func and Var constructors to give them a
    // name for debugging purposes.
    Func gradient("gradient");
    Var x("x"), y("y");
    gradient(x, y) = x + y;
 
    // Realize the function to produce an output image. We'll keep it
    // very small for this lesson.
    Buffer<int> output = gradient.realize({8, 8});
 
    // That line compiled and ran the pipeline. Try running this
    // lesson with the environment variable HL_DEBUG_CODEGEN set to
    // 1. It will print out the various stages of compilation, and a
    // pseudocode representation of the final pipeline.
 
    // If you set HL_DEBUG_CODEGEN to a higher number, you can see
    // more and more details of how Halide compiles your pipeline.
    // Setting HL_DEBUG_CODEGEN=2 shows the Halide code at each stage
    // of compilation, and also the llvm bitcode we generate at the
    // end.
 
    // Halide will also output an HTML version of this output, which
    // supports syntax highlighting and code-folding, so it can be
    // nicer to read for large pipelines. Open gradient.stmt.html" with your
    // browser after running this tutorial.
    gradient.compile_to_lowered_stmt("gradient.stmt.html", {}, HTML);
 
    // You can usually figure out what code Halide is generating using
    // this pseudocode. In the next lesson we'll see how to snoop on
    // Halide at runtime.
 
    printf("Success!\n");
    return 0;
}